(1) Field of the Invention
This invention relates generally to a single chip driver system and relates more particularly to a single CMOS chip system capable to handle high-voltages for e.g. motor drivers in automotive applications.
(2) Description of the Prior Art
In many applications, e.g. in automotive applications, high voltage (HV) is required for a more effective operation. High voltage (HV) in this context means voltage levels up to 40 Volts. In the past very thick gate oxides were used, e.g. up to 80 nm SiO2 would be needed to handle up to 40 Volts. This caused big manufacturing problems to make these thick gate oxides stable with a good quality. In any case it is a very costly solution and doesn't really fit for ASICs requiring system solutions on a single chip. This is especially important because standard voltages used in today's applications may vary from about 1.3V to more than 100V, depending on the specific application.
In standard CMOS technologies high voltage (HV) is defined as any voltage higher than the nominal (low) voltage, i.e. 5V, 3.3V, or even lower. In the standard CMOS environment, IC designers are more and more frequently confronted with HV problems, particularly at the I/O level of the circuit.
A large range of industrial or consumer circuits either require HV driving capabilities, or are supposed to work in a high-voltage environment. This includes ultrasonic drivers, flat panel displays, robotics, automotive, etc. On the other hand, in the emerging field of integrated micro-systems, MEMS actuators mainly make use of electrostatic forces involving HV voltages having an upper range of 30 to 60 Volts while a lower range is in the order of magnitude of less than 30 Volts. Last but not least, with the advent of deep sub-micron and/or low-power technologies, the operating voltage tends towards levels ranging from 1V to 2.5V, while the interface needs to be compatible with higher voltages, such as 5V.
For all these categories of applications, it is usually preferable to perform most of the signal processing at low voltage, while the resulting output requires a higher voltage level. Solving this problem requires some special actions at three levels: technology, circuit design and layout.
Electrical motor drivers are typical applications of single chip systems. There are various patents available to drive electrical motors from a single chip. Until now the upper limit of the voltage level is still too low for many applications as e.g. in the automotive sector.
U.S. Pat. No. 6,680,590 to Inoue et al. describes a vibration motor obtaining a FAST signal when r.p.m. of the motor is faster than reference speed, whereby an output-driving circuit is controlled by the FAST signal to omit parts of the powering periods of respective phases. The motor thus controls the r.p.m. and increases torque ripple generated from the motor. As a result, vibration magnitude increases and insufficient vibration due to downsizing of the motor can be compensated by the control system. A motor driver can be formed with a one chip semiconductor device, so that the number of exterior components is reduced and the motor can be downsized and have light weight.
U.S. Pat. No. 5,013,899 to Collins. discloses a microprocessor-controlled scanning system having a scanning element, which is driven by a three-phase DC motor having a low quiescent current motor driver circuitry. A bus driver chip normally used to drive a computer memory bus is novelly used in place of a prior art triple half-bridge circuit to source and sink the drive windings of the motor, thus significantly reducing the drive circuitry power requirement